1. Field of the Invention
This invention relates generally to electrosurgical devices, and in one particular aspect, provides a serpentine electrode which is adapted for removing tissue, and for sliding over a tissue surface for ablation and/or coagulation.
Electrocautery has been in use for many years as a surgical technique. For example, it is known to use electrosurgical cutting elements in transcervical fibroid removal to sever and remove uterine tissues. Such severing of tissues requires electrical potentials at high voltage settings, typically being an alternating current of between about 100 KHz and 2.2 GHz, and between about 500 and 16,000 volts. This energy is transmitted from a small cutting surface of a surgical instrument to the tissues at the surgical site. Uterine cavity distension can facilitate this electrosurgical procedure, typically with a nonconductive fluid such as sorbitol-mannitol or the like under sufficient pressure to separate the walls of the uterus and render the surgical site suitable for optical fiber observation. The cutting surface usually consists of a wire or other solid shape, and the transmission of current to the tissue is often monopolar, with the circuit completed by a conductive pad applied to the patient's skin.
More recently, bipolar electrocautery systems and devices have been proposed for use in conductive solutions such as saline. These bipolar devices often incorporate a return path through a relatively large conductive surface near the cutting wire, so that the energy is concentrated only at the cutting surface adjacent the target tissues.
In both monopolar and bipolar systems, heat generated from the resistance of tissues to the concentrated flow of electrical current is high enough to vaporize cells near the cutting surface. Thus, a cut is made with very little physical resistance from the small cutting surface. Small diameter electrosurgical cutting wires minimize total physician effort, particularly when severing relatively large amounts of tissues. Heat from the cutting element can also cauterize smaller blood vessels, so that visibility remains reasonably good.
Electrosurgical resistance heating may also be used at much lower power densities to coagulate bleeding tissues, and to kill selected areas of tissue through ablation. Ablation/coagulation electrodes are generally much larger in surface area and cross-section than electrosurgical cutting wires. These large, specialized electrodes treat broad surfaces without penetrating the tissue. Electrosurgical ablation probes are used within the uterus to kill the endometrial lining, often using a conductive roller ball or barrel to heat a wide swath of tissue with each stroke. Once again, distention with a conductive or nonconductive medium can help expose the uterine lining.
While these differing electrosurgical methods have been largely successful, they suffer from significant disadvantages. In particular, it is often desirable to use a cutting device for resection of fibroids, and during the same procedure, to cauterize any bleeding blood vessels or to ablate alternative portions of the uterus. Generally, this requires removal of the resection wire from the distended uterus and insertion of a roller ball or roller barrel electrode. This electrode removal and replacement significantly increases the time required for each procedure, and can complicate the fluid pressurization method and system to maintain distention throughout both procedures.
It has previously been proposed to use a single electrode structure for both cutting and ablation. Unfortunately, the drag from known large ablation electrodes adds substantially to physician effort during removal of tissues. In addition, high power settings associated with vaporization and severing of tissues results in a build-up of hardened electrosurgical debris and tissue on the rolling ablation elements. This tissue and debris build-up can prevent rolling and interfere with visibility. While two different electrode structures can be included in a single probe, this adds to probe cost, complexity, and size, and may result in a less maneuverable device.
In light of the above, it would be advantageous to provide improved electrodes, electrosurgical systems, and electrosurgical methods. It would be particularly advantageous to provide enhanced structures and techniques to facilitate resection, ablation, and coagulation with a single electrode. Preferably, these improvements would minimize physician effort and avoid tissue adherence effects, but would not significantly increase complexity or cost over known electrosurgical systems.
2. Description of the Background Art
U.S. Pat. No. 5,197,964 describes a bipolar instrument having a stationary electrode and a movable electrode. U.S. Pat. No. 5,192,280 describes a pivoting multiple loop bipolar cutting device, and U.S. Pat. No. 5,528,610 describes a grooved slider electrode for a resectoscope, in which the electrode may have a number of different configurations.
U.S. Pat. No. 5,277,201 describes an endometrial ablation apparatus and method. U.S. Pat. No. 5,507,743 is directed toward a coiled radio frequency electrode treatment apparatus. U.S. Pat. No. 5,100,423 describes an ablation catheter, while U.S. Pat. No. 5,431,649 describes an alternative method and apparatus for radio frequency ablation. European Patent Application No. 0,316,995 is also relevant.